U.S. patent number 4,044,266 [Application Number 05/701,498] was granted by the patent office on 1977-08-23 for apparatus for ion-implantation in elements, especially discs of semi-conducting material.
This patent grant is currently assigned to Danfysik A/S. Invention is credited to Einar Jespersen, Ottar Asbjorn Skilbreid.
United States Patent |
4,044,266 |
Jespersen , et al. |
August 23, 1977 |
Apparatus for ion-implantation in elements, especially discs of
semi-conducting material
Abstract
An apparatus for ion-implantation in elements, especially discs
of semi-conducting material, in which a vacuum container has an end
wall which has lock means by which the elements may be passed from
the outside of the container to a position in the end wall, where
one of its surfaces is exposed to the vacuum space in the container
and treated by ions. The lock means includes a rotatable slide
valve mounted between two parallel walls in one of which an
aperture to the outer atmosphere is provided and in the second of
which an aperture to the inner space of the container is provided.
A number of apertures, corresponding to the said apertures in the
walls, are provided in the slide value. The elements are positioned
in one of the apertures in the slide valve, and by its rotation,
conveyed to the wall aperture opening into the vacuum space. In the
two parallel walls, two sets of cavities are provided, one
encircling the other, each of which is connected to a separate
vacuum source. When an element is conveyed from the wall aperture
connected with the atmosphere to the wall aperture connected with
the vacuum space, it passes the two systems of cavities, so that
air in all value apertures of the lock means will be successively
evacuated to the vacuum sources.
Inventors: |
Jespersen; Einar (Roskilde,
DK), Skilbreid; Ottar Asbjorn (Lyngby,
DK) |
Assignee: |
Danfysik A/S
(DK)
|
Family
ID: |
8119131 |
Appl.
No.: |
05/701,498 |
Filed: |
July 1, 1976 |
Foreign Application Priority Data
Current U.S.
Class: |
250/441.11;
250/492.2 |
Current CPC
Class: |
B23K
17/00 (20130101); H01J 37/18 (20130101) |
Current International
Class: |
B23K
17/00 (20060101); H01J 37/18 (20060101); H01J
37/02 (20060101); G01N 021/00 (); G01N 023/00 ();
G21G 005/00 () |
Field of
Search: |
;250/441,492A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Smith; Alfred E.
Assistant Examiner: Grigsby; T. N.
Attorney, Agent or Firm: Hill, Gross, Simpson, Van Santen,
Steadman, Chiara & Simpson
Claims
We claim:
1. Apparatus for ion-implantation in elements such as discs of
semi-conducting material, comprising:
a. a high vacuum container;
b. an ion source and ion acceleration means disposed in said
container;
c. a first disc forming a wall of said container and a second disc
secured in spaced relation thereto, said discs having stationary
plane parallel walls facing each other, said first disc having a
first aperture leading to the interior of said container and said
second disc having a second aperture leading to the atmosphere;
d. a slide valve having parallel surfaces slidably abutting said
parallel walls, said slide valve having at least one throughgoing
aperture for receiving an element through said second aperture, and
for moving it into registration with said first aperture and back;
and
e. evacuated cavities in said discs and disposed to intercept the
air introduced through said second aperture and leaking along said
parallel valve surfaces, whereby air is prevented from reaching
said first aperture.
2. Apparatus according to claim 1 having at least two sets of said
evacuated cavities, each of which sets is adapted to be connected
with a separate vacuum source, one set of said cavities surrounding
the other set in such a way that any air leaking toward said
aperture has to pass through both sets of cavities in
succession.
3. Apparatus according to claim 1, said cavities comprising grooves
in the parallel stationary walls of said discs.
4. Apparatus according to claim 3, said cavities comprising an
annular groove in each of said walls and surrounding said first
aperture.
5. Apparatus according to claim 1, said slide valve being a
circular disc rotatable about its axis, said aperture or apertures
in said slide valve being disposed on a circle concentric with said
axis, said first and second apertures being disposed in
substantially diametrically opposite relationship, one of said
cavities having a portion extending along the periphery of said
slide valve and including a connecting groove spanning said slide
valve, and the other of said cavities being annular surrounding
said first aperture.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus for ion-implantation in
elements, the apparatus including a novel lock or transfer means
for inserting and removing the elements from a high vacuum
space.
2. Prior Art
In the manufacture of semi-conducting components, such as
transistors, there is used a semi-conducting material, such as
silicon, which is activated. The activation consists in introducing
small amounts of another substance, e.g. boron. This additive is to
"dope" the elements to a certain depth under the surface, and the
depth depends on the purpose and the use of the components which
are to be manufactured from the element.
The doping has previously been carried out by the diffusion method.
During recent years the so-called ion-implantation method has been
used which opens up the possibility of manufacturing new types of
components and a substantially greater homogeneity of the finished
products.
For the implantation method, an apparatus may be used, having a
lock means arranged in one end of a vacuum space, and an ion-source
and ion-acceleration means are arranged in the other end. In the
ion-source, the dope-material is ionized. The ions are accelerated
to the necessary speed and are fired on the element which is
situated in the lock means, a surface of the element being exposed
toward the inner space of the vacuum container.
In the use of such method, it has been difficult to maintain the
high vacuum which is necessary for obtaining a satisfactory result,
due to the fact that air leaks into the vacuum space from the outer
atmosphere through the lock means.
Apparatus is known which uses a circular disc having a plurality of
apertures arranged in a ring, an element which is to be treated
being arranged in each of said apertures. Thereafter the lock means
is airtightly closed and evacuated, so that all the cavities in the
lock means have substantially the same pressure as the vacuum
container. When all the elements have been treated, the lock means
is opened and the elements are removed.
In order to increase the working speed and the capacity of the
apparatus it is desirable that the elements be introduced and
removed continuously without stopping the process for replacing a
treated set by a new set and evacuating the lock means. However, in
such a continuous process lines 24 and 25 will pass into the
apertures of the lock means during loading, and will be transported
to the aperture leading to the inner space of the vacuum container.
If each element is in contact with the vacuum space for ten
seconds, a relatively quick interchange of elements and a
corresponding quick movement of the slide valve will take place,
whereby relatively large amounts of air is introduced into the lock
means. A large portion of this air may be removed by evacuating the
apertures in the slide valve during the working of the apparatus,
but even if the lock means have been manufactured with the utmost
accuracy, small spaces between the surfaces of the slide valve and
the stationary surfaces will exist through which air may leak from
the aperture connected with the outer atmosphere to the aperture
connected with the vacuum space in the container.
SUMMARY OF THE INVENTION
The object of the invention is to provide an apparatus of the type
in question which is so built that the said undesired air may be
removed before it can reach the aperture connected with the vacuum
space in the container.
According to the invention, cavities are so arranged in the
apparatus that air, introduced through the aperture connected with
the outer atmosphere and leaking between the surfaces of the slide
valve and the surfaces of the stationary walls, is prevented from
reaching the aperture connected with the inner space of the
container without passing one of the said cavities, the cavities
being connected to a vacuum source.
By this construction, air from the aperture connected with the
outer atmosphere and carried in a valve aperture, as well as air
passing between the surfaces in the lock means will sooner or later
reach the said evacuated cavities and be evacuated from these.
Another object of the invention is to provide an apparatus of the
said kind in which two or more sets of cavities are provided, each
of which is connected with a separate vacuum source, the said
cavities surrounding each other in such a way that air passing
toward the aperture connected with the inner space of the container
has to pass the sets of cavities in succession.
Still another object of the invention is to provide an apparatus of
the said kind in which the cavities comprise grooves in the
parallel, stationary walls.
A further object of the invention is to provide an apparatus of the
said kind in which one set of cavities comprises an annular groove
in each of the parallel, stationary surfaces surrounding the
aperture connected with the inner space of the vacuum
container.
A still further object of the invention is to provide an apparatus
of the said kind in which a cavity is provided along the periphery
of the slide valve and connected with a groove extending across the
area inside the said cavity, the cavity and the groove being
connected with a vacuum source, the aperture connected with the
inner space of the container being surrounded by an annular groove
which is connected with another vacuum source.
On the Drawings:
The invention is described below with reference to the accompanying
drawing, in which
FIG. 1 is a plan view of a stationary wall for a lock means
according to the invention taken along line 1--1 of FIG. 2; and
FIG. 2 is a cross-sectional view through the lock means taken along
the line 11--11 in FIG. 1.
As Shown on the Drawings:
A lock means shown in FIG. 2 comprises two circular discs 1 and 2,
preferably of plastic material, and a circular disc 3, e.g. a steel
plate, mounted between the discs 1, 2 and rigidly connected to a
shaft 4, so that it may rotate about the axis 5 of the latter. The
disc 1 is an end wall of a high vacuum container 1A (shown
fragmentarily in the drawing), and the shaft 4 is situated in the
inner space of said container and is connected with drive means
(not shown in the drawing) for rotation of the slide valve 3. A
sealing ring 6 is mounted between the shaft 4 and the disc 1.
In the disc 1 a circular aperture 7 is provided, and this aperture
is connected with the vacuum space in the said container 1A. In the
disc 2 a corresponding circular aperture 8 is provided which is
connected with the outer atmosphere line 15 at an angularly offset
point, e.g. diametrically opposite.
The slide valve 3 has six circular apertures 9 whose location
relative to the discs 1 and 2 are shown in FIG. 1 in dot-and-dash
lines. The location of the aperture 7 in the disc 1 is shown in
line segments. All the apertures are arranged on a circle 10, the
center of which is concentric with the pivotal axis 5 of the slide
valve 3.
A sealing ring 11 is arranged between the peripheral rim portions
of the discs 1 and 2, so that an annular cavity 12 is provided
between the sealing ring 11 and the periphery of the slide valve 3,
which cavity 12 by means of a pair of radial grooves 13 in each of
the discs 1 and 2 is connected to a central cavity 14 which is
constituted by two recesses in the discs 1 and 2 and which is
connected with the bore for the shaft 4.
The portion of the annular cavity 12 bounded by the ring 11 and the
slide valve 3 is indicated by the larger dot-dash circles.
A groove 15 surrounds the aperture 7 in the disc 1, and a
corresponding groove 17 is provided in the disc 2, said grooves
having radial portions 16.
The system of passages which is constituted by the cavity 12, the
grooves 13, and the cavity 14 is connected with a first vacuum pump
a, and the passages 15 and 17 are connected with a second vacuum
pump b.
During the use of the apparatus, circular element, such as a disc
of semi-conducting material, is placed in each of the apertures 9
in the slide valve 3, and for each 60.degree. of rotation of the
slide valve, a finished element is returned to and removed through
the aperture 8, and a new element is introduced through such
aperture. At the following positioning of the slide valve, a new
element is conveyed to the aperture 7 and is the exposed to ion
treatment in the vacuum space of the container.
As shown in FIG. 1, the aperture 7 which is connected with the
inner space of the vacuum container is surrounded by two sets of
cavities of which the first set is constituted by the grooves 15-17
in each of the stationary surfaces, whereas the second set of
cavities is constituted by the peripheral cavity 12, the grooves
13, and the cavity 14. Air leaking from the aperture 8 in a
direction toward the aperture 7 in the spaces between the parallel
surfaces of the slide valve and the stationary surfaces of the
discs 1 and 2 will sooner or later reach the cavity 12 or the
grooves 13 and will be evacuated by means of the vacuum pump a
connected to this cavity system. Any air passing the said system of
cavities will sooner or later reach one of the grooves 15-17 and
will be evacuated by the vacuum pump B connected to these
grooves.
The apertures 9, by the rotation of the slide valve 3 from the
aperture 8 to the aperture will initially pause at and pass one of
the grooves 13 and later on pause at and pass one of the grooves
16, and the apertures will therefore be evacuated on their way to
the aperture 7 for either direction of incremental valve
rotation.
By the structure which is described above, vacuum conditions are
maintained in all the cavities in the lock means so that the
necessary vacuum can be maintained in the vacuum container.
* * * * *